Interconnect assemblies and methods

RELATED APPLICATIONS

0001This application is related to U.S. Pat. application Ser. No. 09/114,589, concurrently filed on Jul. 13, 1998, now issued U.S. Pat. No. 6,330,164, and continuation application Ser. No. 09/971,981, now issued U.S. Pat. No. 6,664,628.

FIELD OF THE INVENTION

0002The present invention relates to interconnect assemblies and methods for making and using interconnections and more particularly to interconnect assemblies for making electrical contact with contact elements on a semiconductor integrated circuit in either a temporary or permanent manner. More particularly, the present invention relates to techniques and assemblies for making interconnections to semiconductor devices to perform test and/or burn-in procedures on the semiconductor devices or to make permanent interconnections to the semiconductor devices.

BACKGROUND OF THE INVENTION

0003There are numerous interconnect assemblies and methods for making and using these assemblies in the prior art. For example, it is usually desirable to test the plurality of dies on a semiconductor wafer to determine which dies are good prior to packaging them and preferably prior to their being singulated from the wafer. To this end, a wafer tester or prober may be advantageously employed to make a plurality of discrete pressure connections to a like plurality of discrete contact elements (e.g. bonding pads) on the dies. In this manner, the semiconductor dies can be tested prior to singulating the dies from the wafer. The testing is designed to determine whether the dies are non-functional (“bad”).

0004A conventional component of a wafer tester or prober is a probe card to which a plurality of probe elements are connected. The tips of the probe elements or contact elements effect the pressure connections to the respective bonding pads of the semiconductor dies. <figref idref="DRAWINGS">FIG. 1</figref> shows an interconnect assembly <b>500</b> which is an example of a probe card in the prior art. The probe pins or contact elements <b>524</b> make connections to bonding pads <b>526</b> on the semiconductor wafer <b>508</b>. The probe card assembly includes several components which are assembled together, including the probe card <b>502</b>, the interposer <b>504</b>, and the space transformer <b>506</b>. The probe card <b>502</b> is typically a printed circuit board which includes circuit traces to various electrical components which are used in performing the electrical tests of the semiconductor die being probed. Contact elements <b>510</b> on the probe card <b>502</b> make contact with the bonding pads <b>526</b> through a series of intervening layers which include the interposer <b>504</b> and the space transformer <b>506</b> as shown in FIG. <b>1</b>. The interposer <b>504</b> provides for a resilient, springlike positioning in the vertical or z direction in order to provide adequate contact for all contact elements at the bonding pads regardless of the length of the contact elements used on the intervening layers, such as the contact elements <b>524</b> which resemble springs. The space transformer <b>506</b> performs a pitch reduction and is also the substrate on which resilient contact elements are disposed. Further details concerning the probe card assembly <b>500</b> shown in <figref idref="DRAWINGS">FIG. 1</figref> may be found in PCT International Publication No. WO 96/38858.

0005<figref idref="DRAWINGS">FIG. 2A</figref> shows in more detail an interposer assembly <b>300</b> having a substrate <b>302</b> on which resilient contact elements are attached, including contact elements <b>312</b>, <b>314</b>, <b>316</b>, and <b>318</b>. Contact elements <b>312</b> and <b>316</b> are electrically coupled from one side of interposer <b>300</b> to the other side by a through connect <b>304</b>A, and contact elements <b>314</b> and <b>318</b> are electrically coupled by a through connect <b>306</b>A. Examples of these resilient contact elements include any of a number of different spring type elements, including those described in the PCT International Publication No. WO 96/38858. When the interposer is used in an assembly such as the assembly <b>500</b> of <figref idref="DRAWINGS">FIG. 1</figref>, the resilient contact elements are flexed to a compressed state in which their vertical heights are reduced. This flexed state results in a force which drives the contact elements into their corresponding connection points, such as the bonding pads <b>526</b>. <figref idref="DRAWINGS">FIGS. 2B and 2C</figref> show an alternative interposer structure of the prior art. The interposer <b>300</b>A includes a substrate <b>302</b>A. Two resilient contact elements <b>312</b>A and <b>314</b>A are attached to one surface of the substrate <b>302</b>A. The resilient contact elements of the bottom portion of the substrate <b>302</b>A are not shown in this figure. The resilient contact elements on the upper surface of the substrate <b>302</b>A are protected by a channel structure <b>302</b>B which surrounds the resilient contact elements <b>312</b>A and <b>314</b>A. This can be seen from the top view of the interposer <b>300</b> which is shown in FIG. <b>2</b>C. The channel <b>302</b>B protects the resilient contact elements within the channel but is not designed to contact another substrate, and the channel <b>302</b>C protects resilient contact elements <b>314</b>B but is not designed to contact another substrate.

0006<figref idref="DRAWINGS">FIG. 3A</figref> shows another example of an interposer of the prior art. The substrate <b>334</b> is placed over the interconnection elements <b>332</b> so that the interconnection elements <b>332</b> extend through the holes <b>336</b>. The interconnection elements <b>322</b> are loosely held within the substrate by a suitable material <b>338</b>, such as an elastomer which fills the holes <b>336</b> and which extends from the top and the bottom surfaces of the support substrate. <figref idref="DRAWINGS">FIG. 3B</figref> illustrates another interposer structure of the prior art in which the interconnection element within the hole <b>336</b> is attached to (e.g. by soldering) the middle portions of the holes <b>366</b> in the substrate <b>364</b>.

0007<figref idref="DRAWINGS">FIG. 4</figref> illustrates another interconnect assembly of the prior art. This interconnect assembly is sometimes referred to as a cinch connector <b>400</b>. As shown in <figref idref="DRAWINGS">FIG. 4</figref>, two contact elements <b>406</b> and <b>407</b> are disposed on a substrate <b>401</b> in order to make contact with two other contact elements <b>408</b> and <b>409</b> which are disposed on another substrate <b>402</b>. The intermediate layer <b>403</b> includes holes <b>404</b> and <b>405</b>. The hole <b>404</b> is positioned between the contact elements <b>407</b> and <b>408</b>, and the hole <b>405</b> is positioned between the contact elements <b>407</b> and <b>409</b>. Each hole includes a resilient material which is used to make contact between its respective contact elements as shown in FIG. <b>4</b>. When the substrates <b>401</b> and <b>402</b> are pressed together, the contact elements or pads <b>406</b> and <b>408</b> move toward each other as do the contact elements <b>407</b> and <b>409</b>. The movement is stopped when each element comes into mechanical contact with the intermediate layer <b>403</b>, and electrical contact is established by the respective conductive spring which is disposed between the two contact elements.

0008As can be seen from the foregoing discussion, the use of resilient contact elements to make contacts to bonding pads or to other contact elements allows for tolerance in the vertical or z direction such that most if not all contact elements will be able to make contact even if their lengths vary slightly. However, this tolerance sometimes leads to the destruction of resilient contact elements as they are compressed too much in the vertical direction. While the assemblies shown in <figref idref="DRAWINGS">FIGS. 2B and 2C</figref> and in <figref idref="DRAWINGS">FIG. 3A</figref> may tend to protect resilient contact elements, they do not and are not intended to define a position in which all contact elements should have made contact vertically. The cinch connector of <figref idref="DRAWINGS">FIG. 4</figref> does tend to protect the resilient contact elements by preventing the substrates <b>401</b> and <b>402</b> from coming too close together. However, this assembly is relatively complicated due to the requirement of having, in a separate layer, a plurality of holes each of which includes and supports a spring.

0009Thus it is desirable to provide an improved interconnect assembly which may take advantage of the features of a resilient contact element without having too much tolerance in the z direction which could result in the overflexing or destruction of the resilient contact elements. This is particularly important for interconnection over large mating areas (as in semiconductor wafers), where tolerance issues make controlled deflection of interconnect elements difficult.

SUMMARY OF THE INVENTION

0010The present invention provides a plurality of interconnect assemblies and methods for making and using these assemblies. In one example of the present invention, an interconnect assembly includes a substrate and a resilient contact element having at least a portion thereof which is capable of moving to a first position. The resilient contact element is disposed on the substrate. A stop structure, also disposed on the substrate, defines the first position in which the resilient contact element is in mechanical and electrical contact with another contact element.

0011Typically in this example, the another contact element is disposed on another substrate, and the stop structure defines a minimum separation between the substrate and the another substrate when the resilient contact element is in mechanical and electrical contact with the another contact element.

0012According to another example of the present invention, an interconnect assembly includes a first substrate and a first contact element which is disposed on the first substrate. A stop structure defines a first position of a first resilient contact element which is disposed on a second substrate when the resilient contact element is in mechanical and electrical contact with the first contact element. Typically, the resilient contact element has at least a portion thereof which is capable of moving to a first position when the resilient contact element is compressed.

0013The present invention also includes various methods, including a method for forming an interconnect assembly. In this method, a resilient contact element is formed on a substrate. The resilient contact element has at least a portion thereof which is capable of moving to a first position. A stop structure is also formed on the substrate, and it defines the first position when the resilient contact element is in mechanical and electrical contact with another contact element.

0014According to another example of a method of the present invention, a first contact element is formed on a first substrate and a stop structure is also formed on the first substrate. The stop structure defines a first position of a resilient contact element when the resilient contact element is in mechanical and electrical contact with the first contact element.

0015Various other assemblies and methods are described below in conjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

0016The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.

0017<figref idref="DRAWINGS">FIG. 1</figref> shows an example of a probe card assembly in the prior art.

0018<figref idref="DRAWINGS">FIG. 2A</figref> shows an example of an interposer which is an element of a probe card assembly of the prior art.

0019<figref idref="DRAWINGS">FIG. 2B</figref> shows an cross-sectional view of another example of an interposer which may be used in probe card assemblies of the prior art.

0020<figref idref="DRAWINGS">FIG. 2C</figref> shows a top view of the interposer shown in FIG. <b>2</b>B.

0021<figref idref="DRAWINGS">FIG. 3A</figref> shows a cross-sectional view of another example of an interposer of the prior art.

0022<figref idref="DRAWINGS">FIG. 3B</figref> shows a cross-sectional view of another interposer structure of the prior art.

0023<figref idref="DRAWINGS">FIG. 4</figref> shows an example of an interconnect assembly of the prior art.

0024<figref idref="DRAWINGS">FIG. 5A</figref> shows a perspective view according to the invention in which resilient contact elements are disposed on a substrate along with stop structures on the substrate. <figref idref="DRAWINGS">FIG. 5B</figref> shows a perspective view of an embodiment of the invention in which resilient contact elements are disposed with a fan-out on a substrate with stop structures.

0025<figref idref="DRAWINGS">FIG. 6A</figref> shows an example of one embodiment of the present invention (before mechanical and electrical contact is made).

0026<figref idref="DRAWINGS">FIG. 6B</figref> shows the interconnect assembly of <figref idref="DRAWINGS">FIG. 6A</figref> when mechanical and electrical contact has been made.

0027<figref idref="DRAWINGS">FIG. 6C</figref> shows an example of another embodiment of the present invention (before mechanical and electrical contact is made).

0028<figref idref="DRAWINGS">FIG. 6D</figref> shows the interconnect assembly of <figref idref="DRAWINGS">FIG. 6C</figref> when electrical and mechanical contact has been made.

0029<figref idref="DRAWINGS">FIG. 7</figref> shows another example of an interconnect assembly according to the present invention.

0030<figref idref="DRAWINGS">FIG. 8A</figref> shows an example of another embodiment of an interconnect assembly according to the present invention.

0031<figref idref="DRAWINGS">FIG. 8B</figref> shows another example of a stop structure according to the present invention.

0032<figref idref="DRAWINGS">FIG. 9A</figref> illustrates a layer for a die (an integrated circuit) which layer may be used to make stop structures according to the present invention.

0033<figref idref="DRAWINGS">FIG. 9B</figref> illustrates a cross-sectional view through the line <b>9</b><i>b</i>—<b>9</b><i>b </i>of the layer of FIG. <b>9</b>A.

0034<figref idref="DRAWINGS">FIG. 9C</figref> shows the use of the layer of <figref idref="DRAWINGS">FIGS. 9A and 9B</figref> on a substrate in accordance with one embodiment of the present invention.

0035<figref idref="DRAWINGS">FIG. 9D</figref> shows another example of a stop structure for an integrated circuit according to the present invention.

0036<figref idref="DRAWINGS">FIG. 9E</figref> illustrates an example of a sheet of material for forming several stop structures at the same time, each stop structure being similar to the stop structure of FIG. <b>9</b>D.

0037<figref idref="DRAWINGS">FIG. 9F</figref> is a perspective view of stop structures with openings for contact elements which are fanned out from bonding pads.

0038<figref idref="DRAWINGS">FIGS. 10A</figref>, <b>10</b>B, and <b>10</b>C illustrate one method for lithographically forming a contact element and a corresponding stop structure according to one example of the present invention.

0039<figref idref="DRAWINGS">FIG. 10D</figref> illustrates in cross-sectional view the interaction between a lithographically formed contact element, another contact element and a stop structure according to one example of the present invention.

0040<figref idref="DRAWINGS">FIG. 10E</figref> is a top plan view of a die having a variety of stop structures and two rows of resilient contact elements.

0041<figref idref="DRAWINGS">FIGS. 10F through 10M</figref> show, through cross-sectional views, a method for lithographically forming a resilient contact element and a stop structure on a substrate such as an integrated circuit.

0042<figref idref="DRAWINGS">FIG. 11</figref> shows a method of using the interconnect assemblies of the present invention in conjunction with a bellows chuck.

0043<figref idref="DRAWINGS">FIG. 12A</figref> shows an example of the use of an interconnect assembly of the present invention in conjunction with a vacuum chuck.

0044<figref idref="DRAWINGS">FIG. 12B</figref> shows an example of the use of an interconnect assembly according to the present invention in conjunction with a bladder chuck system.

0045<figref idref="DRAWINGS">FIG. 13</figref> shows an example of a stop structure having a circuit element according to one embodiment of the present invention.

0046<figref idref="DRAWINGS">FIG. 14</figref> illustrates two stop structures, each of which includes at least one circuit element according to one example of the present invention.

DETAILED DESCRIPTION

0047The present invention relates to interconnection assemblies and methods and particularly to interconnect assemblies for making mechanical and electrical connection to contact elements on an integrated circuit. The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention. Numerous specific details are described to provide a thorough understanding of the present invention. However, in certain instances, well known or conventional details are not described in order to not unnecessarily obscure the present invention in detail.

0048<figref idref="DRAWINGS">FIG. 5A</figref> shows a perspective view of eight resilient contact elements <b>110</b>, each of which are disposed on a substrate <b>102</b>A. The interconnect assembly shown in <figref idref="DRAWINGS">FIG. 5A</figref> may be formed by any number of methods; for example, the resilient contact elements may be mechanically secured to pads <b>103</b> by a wire bonding operation. Alternatively, the resilient contact elements may be lithographically formed. Also disposed on the substrate <b>102</b>A are a plurality of stop structures. The left row of stop structures <b>105</b> protrudes above the top surface of the substrate <b>102</b>A by a predetermined amount which will typically be the same amount by which the right row of stop structures <b>104</b> protrudes above this top surface. These stop structures are designed to determine/limit the maximum amount of compression or flexing which can occur with the resilient contact elements. Each resilient contact element includes at least a portion thereof which is capable of moving to a first position when the resilient contact element is compressed in a vertical direction towards the top surface of the substrate <b>102</b>A. Each stop structure is sized vertically such that it defines a first position when the resilient contact elements are in mechanical and electrical contact with other contact elements. Each stop structure is designed, in one embodiment, so that its vertical height above the substrate is less than the vertical height of the shortest resilient contact element which statistically is reasonably likely to exist (e.g. the stop's height is less than 99.9% of the heights of possible resilient contact elements).

0049<figref idref="DRAWINGS">FIG. 5B</figref> shows a perspective view of another embodiment of the invention in which an in-line row of bonding pads <b>103</b> are coupled by fan-out traces <b>103</b>A to several resilient contact elements <b>110</b>A. The fan-out traces <b>103</b>A allow a spatial distribution of the resilient contact elements from the in-line row without requiring the use of resilient contact elements having different lengths (as in the case of <figref idref="DRAWINGS">FIG. 5A</figref> where the resilient contact elements <b>110</b> have different lengths in order to make contact to spatial dispersed elements). Each of the bonding pads <b>103</b> is coupled electrically to a corresponding fan-out trace <b>103</b>A which is electrically coupled to a corresponding pad <b>103</b>B, and each resilient contact element <b>110</b>A is electrically and mechanically coupled to a corresponding pad <b>103</b>B. Several stop structures <b>105</b> are disposed on the surface of the integrated circuit <b>102</b>B.

0050<figref idref="DRAWINGS">FIG. 6A</figref> shows an example of an interconnect assembly <b>601</b> of the present invention. The interconnect assembly <b>601</b> includes a substrate <b>602</b> and a substrate <b>603</b>. The substrate <b>603</b> includes two contact elements <b>604</b> and <b>605</b> which are attached to the substrate <b>603</b> and thereby disposed on the substrate <b>603</b>. The substrate <b>602</b> includes two stop structures <b>606</b> and <b>607</b> which may be disposed in relative proximity to the resilient contact elements <b>608</b> and <b>609</b>. These resilient contact elements may be the spring interconnect elements described in the PCT International Publication No. WO 96/38858. Each resilient contact element includes a tip or farthest extent which typically extends beyond the top of the respective stop structure as shown in FIG. <b>6</b>A. For example, the tip <b>608</b>A of the resilient contact element <b>608</b> extends beyond the top of the stop structure <b>606</b> such that the total vertical length of the resilient contact member <b>608</b> exceeds the total vertical length of the stop structure <b>606</b>. The height of the stop structure is predetermined in order to define a first position when the resilient contact element is in mechanical and electrical contact with another contact element. Further, the stop structure's height defines a separation between one substrate <b>602</b> and the other substrate <b>603</b> when the resilient contact element is in mechanical and electrical contact with another contact element, such as the contact elements <b>604</b> and <b>605</b>. This is further shown in <figref idref="DRAWINGS">FIG. 6B</figref> in which the substrates <b>602</b> and <b>603</b> have been forced together to create the interconnect assembly <b>601</b>A. As can be seen from <figref idref="DRAWINGS">FIG. 6B</figref>, the stop structures <b>606</b> and <b>607</b> are in mechanical contact with the substrate <b>603</b>; in particular, the top surface of each stop structure is mechanically abutting the top surface of the substrate <b>603</b>. This defines the first position of the tip <b>608</b>A and the tip <b>609</b>A of the resilient contact elements <b>608</b> and <b>609</b> respectively as they make contact with the contact elements <b>604</b> and <b>605</b> respectively.

0051It will be appreciated that the interconnect assembly <b>601</b> may be used in a number of different contexts. For example, the substrate <b>602</b> may be part of a probe card assembly which is coupled to a wafer prober or wafer tester and the substrate <b>603</b> may be a semiconductor integrated circuit or a plurality of integrated circuits on a semiconductor wafer. Alternatively, substrate <b>602</b> may be part of a semiconductor integrated circuit or a plurality of integrated circuits on a semiconductor wafer. In this case, the resilient contact elements will typically be coupled to bonding pads or other contact elements on the integrated circuit, and the stop structures will be attached to the top surface of the integrated circuit. The substrate <b>603</b> may be part of a probe card structure which is designed to make electrical contact with the various resilient contact elements in order to test or burn-in the integrated circuit or a plurality of integrated circuits on a semiconductor wafer. Alternatively, the substrate <b>603</b> may be part of a package assembly which is used to make permanent contact through the resilient contact elements, such as the elements <b>608</b> and <b>609</b> shown in FIG. <b>6</b>A.

0052<figref idref="DRAWINGS">FIGS. 6C and 6D</figref> show another example of the present invention which uses straight (cantilever-style) resilient contact elements <b>608</b>B and <b>609</b>B. These straight resilient contact elements are secured to the substrate <b>602</b> and bend to a compressed state as shown in <figref idref="DRAWINGS">FIG. 6D</figref> when the substrate <b>602</b> is pressed towards the substrate <b>603</b>. The stop structures <b>606</b> and <b>607</b> determine the separation between the two substrates and determine the amount of compression of each resilient contact element when it is brought into mechanical and electrical contact with its corresponding pad.

0053<figref idref="DRAWINGS">FIG. 7</figref> shows an example of another interconnect assembly according to the present invention. The interconnect assembly <b>621</b> of <figref idref="DRAWINGS">FIG. 7</figref> includes a substrate <b>622</b> and a substrate <b>623</b>. Two resilient contact elements <b>628</b> and <b>629</b> are attached to a surface of the substrate <b>622</b> in order to make contact with the contact elements <b>624</b> and <b>625</b> respectively of the substrate <b>623</b>. Two stop structures <b>626</b> and <b>627</b> are also attached to the substrate <b>623</b> and are positioned relatively proximately adjacent to the corresponding contact elements <b>624</b> and <b>625</b>. When the substrate <b>622</b> and <b>623</b> are forced together, the resilient contact elements <b>628</b> and <b>629</b> will flex to a position determined by the height of the stop structures. In one particular embodiment, the height of the stop structure may be from approximately 5 to 40 mils and the height of a resilient contact element before being compressed may be approximately 45 mils. The particular height of the stop structure relative to the height of the resilient contact element before compression will depend in part on the ability to control the planarity of the tips of the various resilient contact elements before compression. If this planarity can be controlled to great precision, then the height of the stop structure may be only slightly less than the height of a resilient contact element before compression. On the other hand, smaller stop structures provide a larger tolerance for error in forming an array of resilient contact elements to a particular height. The height of a stop structure is typically less than 150 mils and preferably less than 40 mils.

0054It will be appreciated that the present invention may be used with a large or small number of resilient contact elements and a number of stop structures disposed on the same or a different substrate. The invention may be used with a single (singulated) IC with a stop structure and a resilient contact element or with IC's on a semiconductor wafer where each such IC includes at least one stop structure and a resilient contact element. Each resilient contact element may have a corresponding stop structure (e.g. a post-like stop structure as in <figref idref="DRAWINGS">FIG. 5B</figref>) or one stop structure may be shared by several resilient contact elements (as shown in FIG. <b>9</b>D). Furthermore, it will be appreciated that the contact elements and the resilient contact elements are coupled to various circuit elements, whether these circuit elements are disposed on the integrated circuit being tested or in a probe card circuit or in a circuit used in a finally assembled system which includes the packaged integrated circuit.

0055<figref idref="DRAWINGS">FIG. 8A</figref> illustrates another example of an interconnect assembly according to the present invention. The interconnect assembly <b>801</b> includes a substrate <b>802</b> which is attached to two stop structures <b>805</b> and <b>806</b>. Also attached to the substrate <b>802</b> are two resilient contact elements <b>803</b> and <b>804</b>. It will be appreciated that the substrate <b>802</b> may be part of an integrated circuit or may be part of a probe card assembly or other testing or burn-in apparatus. Each stop structure as shown in <figref idref="DRAWINGS">FIG. 8A</figref> includes an adhesive layer and a covering disposed over the adhesive layer. Stop structure <b>806</b> includes an adhesive layer <b>807</b> disposed on the top surface of the stop structure, and a covering <b>809</b> is disposed over the adhesive <b>807</b>. This covering may be layer such as a foil or a plastic which may be peeled away or otherwise removed from the adhesive. Similarly, the stop structure <b>805</b> includes an adhesive layer <b>808</b> and a covering layer <b>810</b>. The coverings may be peeled away in order to expose the adhesive and then the adhesive may be used to attach the stop structure as well as the rest of the assembly <b>801</b> onto another object; such as another substrate. For example, the substrate <b>802</b> may be attached to an integrated circuit (not shown) such that the bonding pads of the integrated circuit mate with the resilient contact elements in order to make mechanical and electrical contact with those elements. The substrate <b>802</b> may adhere to the top surface of the integrated circuit by removing the coverings on the top of the stop structures and by pressing the substrate <b>802</b> down towards the integrated circuit such that the adhesive on the stop structures is brought into contact with the top surface of the integrated circuit. Thus, the adhesive layers on the tops of the stop structures bond substrate <b>802</b> to the integrated circuit and cause the resilient contact elements to be secured into mechanical and electrical contact with the corresponding bonding pads or other contact elements on the integrated circuit. In this manner, a package for the integrated circuit may be formed between the substrate <b>802</b> and its corresponding structures and the integrated circuit. It will be appreciated that in this example, the substrate <b>802</b> will include interconnections from the various resilient contact elements towards other contact points to allow interconnection to other electrical components outside of the packaged assembly formed by the substrate <b>802</b> and the integrated circuit which is attached to the substrate.

0056Another use of the interconnect assembly <b>801</b> of <figref idref="DRAWINGS">FIG. 8A</figref> may involve the case where the substrate <b>802</b> is itself an integrated circuit, and the resilient contact elements <b>803</b> and <b>804</b>, as well as other contact elements necessary to make connections, are attached to the various bonding pads or other contact elements on the integrated circuit. The stop structures may be attached to the top surface of the integrated circuit as shown in FIG. <b>8</b>A. After the coverings above the adhesive layers are removed, the integrated circuit may be pressed against another wiring substrate in order to make electrical contact between the circuitry in the integrated circuit in the substrate <b>802</b> in this example and various outside electrical components through the another substrate. This another substrate may be part of a probe card assembly or a burn-in assembly or may be part of a final integrated circuit package which includes interconnections to the “outside” environment.

0057<figref idref="DRAWINGS">FIG. 8B</figref> shows an alternative embodiment of a stop structure <b>821</b> in which adhesive layers are applied to the top and bottom layers of the stop structure <b>822</b>. The adhesive layer <b>824</b> is formed on the top surface of the stop structure <b>822</b>, and a covering <b>826</b> which is removable is placed on this adhesive. Another adhesive layer <b>823</b> is formed on the bottom surface of the stop structure <b>822</b> and is covered by the covering <b>825</b>. This stop structure may be formed in a sheet or film and applied to a substrate in order to form a plurality of stop structures on a substrate. This will be further described in conjunction with <figref idref="DRAWINGS">FIGS. 9A</figref>, <b>9</b>B, and <b>9</b>C.

0058A layer <b>903</b> shown in <figref idref="DRAWINGS">FIG. 9A</figref> has two rows of openings in a sheet or film; these openings are designed to surround at least one resilient contact element as shown in FIG. <b>9</b>C. <figref idref="DRAWINGS">FIG. 9A</figref> shows four openings <b>905</b>, <b>907</b>, <b>909</b>, and <b>911</b> formed in the sheet or film. The layer <b>903</b> is, in the embodiment shown in <figref idref="DRAWINGS">FIG. 9A</figref>, part of a sheet which is designed to fit on a semiconductor wafer <b>902</b> of integrated circuits. The layer <b>903</b> may be formed from any of a number of possible materials, including for example, a polyimide material. The openings may be etched or punched or cut into the layer <b>903</b>. These openings are formed in the layer in order to create openings for contact elements on the integrated circuits of the semiconductor wafer (or for contact elements on another type of substrate). It will be appreciated that in an alternative embodiment, the layer <b>903</b> may be designed to be applied to and to cover only a single integrated circuit and hence will not be applied to cover multiple IC's on a wafer. The line <b>9</b><i>b</i>—<b>9</b><i>b </i>shown in <figref idref="DRAWINGS">FIG. 9A</figref> shows a cross-sectional view of the layer <b>903</b>, which cross-sectional view is shown in FIG. <b>9</b>B.

0059The layer <b>903</b> is applied to a substrate <b>915</b> as shown in FIG. <b>9</b>C. The openings <b>905</b> and <b>907</b> are for contact elements, such as contact elements <b>912</b> and <b>911</b>. <figref idref="DRAWINGS">FIG. 9C</figref> shows a hybrid structure in which some contact elements, such as contact element <b>912</b>, do not include a resilient contact element and other contact elements, such as contact element <b>911</b>, include a resilient contact element. It will be appreciated that typically, such hybrid structures are not preferred, although they are still within the scope of the present invention. The substrate <b>915</b> may be a semiconductor wafer which includes a plurality of integrated circuits or may be a single integrated circuit or may be a contact or interconnect structure of a probe card assembly or a burn-in test assembly. The layer <b>903</b> may be applied to the substrate <b>915</b> by using an adhesive between the abutting faces of the layer <b>903</b> and the substrate <b>915</b>. In this case, the layer <b>903</b> may be a sheet of material which is formed and then applied to the substrate <b>915</b> with an adhesive between the two abutting surfaces. Alternatively, the layer <b>903</b> may be formed photolithographically on the substrate <b>915</b>; in this case, the layer <b>903</b> may be formed from a negative photoresist which is patterned and cured to hardness to form the stop structure. The layer <b>903</b> may also include an adhesive on its top surface in the same way that the stop structures of <figref idref="DRAWINGS">FIGS. 8A and 8B</figref> include such adhesives. It will be appreciated that the layer <b>903</b> as formed on the substrate <b>915</b> provides stop structures in accordance with the present invention, such as the stop structure <b>916</b> which surrounds the contact element <b>912</b>.

0060It will also be understood that the layer <b>903</b> may be used to hermetically seal the IC which is covered by the layer <b>903</b> such that the IC is protected from environmental conditions (i.e. humidity). For example, if the bottom of layer <b>903</b> is adhesively secured to the IC or is photolithographically formed on the IC, the top of the layer <b>903</b> may be adhesively attached (or otherwise secured) to a substrate, such as a cover, which forms a hermetic seal for the IC.

0061<figref idref="DRAWINGS">FIG. 9D</figref> is a plan view which shows another example of a stop structure which surrounds several resilient contact elements. In particular, <figref idref="DRAWINGS">FIG. 9D</figref> illustrates an IC <b>921</b> having a perimeter stop structure <b>922</b> which surrounds several resilient contact elements <b>923</b>. This perimeter stop structure <b>922</b> may be formed from a sheet which is secured to the top surface of IC <b>921</b> or it may be formed in place (e.g. photolithographically) on the IC <b>921</b>. The top surface of the stop structure <b>922</b> may be coated with an adhesive which is used to secure the stop structure <b>922</b> to a cover or other package.

0062<figref idref="DRAWINGS">FIG. 9E</figref> shows an example of a sheet <b>931</b> containing several perimeter stop structures <b>932</b>, <b>933</b>, <b>934</b> and <b>935</b> which are held together by a web <b>936</b> of interconnecting material. The sheet may be formed from a polyimide material or from epoxy material or other materials. The sheet <b>931</b> may be applied over a wafer of ICs to simultaneously place a perimeter stop structure on each of several ICs on the wafer. The sheet <b>931</b> may be secured to the wafer by an adhesive. It will be understood that the sheet <b>931</b> may contain a stop structure for each IC on a wafer. After the sheet <b>931</b> is applied to the wafer, the web <b>936</b> is typically cut in the normal singulation process in which each IC is cut from the wafer. After singulation, each IC will include a perimeter stop structure as shown in FIG. <b>9</b>D.

0063<figref idref="DRAWINGS">FIG. 9F</figref> shows by perspective view another example of the present invention. In this example, a sheet <b>953</b> is applied to the top surface of a substrate <b>952</b> which may be an IC (or may be a space transformer or other structure). The sheet <b>953</b> includes openings, such as openings <b>956</b> and <b>963</b>, which may be cut or otherwise formed in the sheet <b>953</b>. The openings are aligned with fan-out pads; for example, the opening <b>956</b> in sheet <b>953</b> is aligned over at least a portion of fan-out pad <b>956</b>A to provide the opening over at least a portion of fan-out pad <b>956</b>A. Similarly, the opening <b>963</b> is aligned over at least a portion of fan-out pad <b>963</b>A to provide an opening over this fan-out pad. A resilient contact element, such as element <b>957</b> or <b>964</b>, is mechanically and electrically coupled to its corresponding fan-out pad which is electrically coupled to a fan-out trace, such as trace <b>955</b> or trace <b>962</b>. Each fan-out trace electrically couples its corresponding pad, such as pad <b>954</b> or pad <b>961</b>, to the corresponding fan-out pad. Hence, the resilient contact elements provide dispersed, remote electrical contacts for the in-line row of pads such as pads <b>954</b> and <b>961</b>. Each opening around a resilient contact element provides a stop structure which surrounds the resilient contact element. It will be appreciated that, in an alternative embodiment of <figref idref="DRAWINGS">FIG. 9F</figref>, the sheet <b>953</b> may be replaced by a layer which is formed in place on the top surface of the substrate <b>952</b> (e.g. a patterned layer formed from a photoresist or insulating material (such as silicon dioxide)).

0064<figref idref="DRAWINGS">FIGS. 10A</figref>, <b>10</b>B, and <b>10</b>C illustrate a method for lithographically creating both a resilient contact element and a corresponding stop structure. The process shown in <figref idref="DRAWINGS">FIG. 10A</figref> assumes that a substrate <b>1001</b> is a semiconductor wafer which includes a contact element <b>1002</b> (e.g. a bonding pad) disposed thereon, although the process may be used on other substrates having contact elements. <figref idref="DRAWINGS">FIGS. 10A and 10B</figref> show cross-sectional views taken through the contact element <b>1002</b>, and it will be appreciated that this contact element makes electrical contact with other circuit elements not shown in the integrated circuit which is formed in the substrate <b>1001</b>. A plating layer or surface <b>1000</b> is applied to the top surface of the substrate <b>1001</b>; this plating surface <b>1000</b> may be applied by sputtering a conductive metal onto the substrate <b>1001</b>. This plating surface <b>1000</b> will be used as an electrode in a subsequent electroplating process. A resist layer <b>1003</b> is formed and patterned on the plating surface <b>1000</b> such that an opening in the resist layer exists over the contact element <b>1002</b>. A first metal layer <b>1004</b> is then deposited and patterned over the contact element <b>1002</b> (and the plating surface <b>1000</b>) in the opening of the resist <b>1003</b> and also over a portion of the resist <b>1003</b> as shown in FIG. <b>10</b>A. Then an electroplating operation is used to form a plated metal layer <b>1005</b> above the metal layer <b>1004</b>. The resist <b>1003</b> and plating surface <b>1000</b> are then stripped, leaving a resilient contact element, and a stop structure <b>1003</b>A is formed near the resilient contact element. A mask may be used to create a pattern for the stop structures in the resist <b>1003</b>A, and then the resist <b>1003</b>A is etched, leaving the stop structure <b>1003</b>A shown in FIG. <b>10</b>B. <figref idref="DRAWINGS">FIG. 10C</figref> shows a top view of the resilient contact element and its corresponding stop structure of FIG. <b>10</b>B.

0065The resilient contact element of <figref idref="DRAWINGS">FIG. 10B</figref> is typically compressible and resilient at its farthest extent away from its base which is attached to the remnant of the plating surface <b>1000</b>. Thus, the flexing (to a lower height) of the resilient contact element does not normally occur at the portion of the element which rises vertically from its base. Consequently, a stop structure for such a resilient contact element should have a height which is higher than all possible resilient contact elements (taking into account the range of heights of such elements due to the tolerance of forming such elements). Various methods for forming lithographically resilient contact elements are described in several applications of the present assignee including co-pending U.S. patent application Ser. No. 09/032,473, filed Feb. 26, 1998 and PCT Patent Publication No. WO 97/43654, published Nov. 20, 1997. These various methods may be used with the present invention to create lithographically formed resilient contact elements with stop structures.

0066<figref idref="DRAWINGS">FIG. 10D</figref> shows an example of an interconnection between a lithographically formed resilient contact element and a contact element <b>1023</b> on another substrate <b>1021</b>. The stop structure <b>1003</b>A is sized (in height above the resilient contact element) to define the separation between the substrate <b>1001</b> and the substrate <b>1021</b> when the two structures are pressed together, and this separation determines the amount of flexing of the resilient contact element, shown by dashed representation <b>1025</b> of the farthest extent of the resilient contact element. The resilient contact element is caused to flex to this point by the contact element <b>1023</b> which is brought into mechanical and electrical contact with the resilient contact element when the substrates <b>1001</b> and <b>1021</b> are pressed together to the point defined by the height of the stop structure <b>1003</b>A.

0067<figref idref="DRAWINGS">FIG. 10E</figref> shows an example of the invention in which two types of stop structures are used on a substrate <b>1031</b>. A row of post-like stop structures <b>1034</b> and a row of post-like stop structures <b>1035</b> and a post-like stop structure are formed on or attached to the substrate <b>1031</b>. Several perimeter-like stop structures <b>1037</b>, <b>1038</b>, <b>1039</b>, <b>1040</b> and <b>1041</b> are formed on or attached to the substrate <b>1031</b>. Typically all these stop structures have the same height above the top surface of substrate <b>1031</b>. Two rows of resilient contact elements <b>1032</b> and <b>1033</b> are disposed on the substrate <b>1031</b>.

0068Another method for lithographically forming resilient contact elements is shown in FIG. <b>10</b>F through FIG. <b>10</b>M. According to this method, the resilient contact elements are formed on a fan-out pad or a fan-out trace, and thus can produce an assembly which is similar to the assembly shown in FIG. <b>5</b>B. This method will make an electrical connection between a contact element <b>1046</b> and a resilient contact element which can contact electrically another contact element on another substrate. It will be appreciated that contact element <b>1046</b> makes electrical contact with other circuit elements not shown and that substrate <b>1045</b> may be part of an IC or part of a test or interconnect assembly (e.g. an interposer, space transformer or probe card). As shown in <figref idref="DRAWINGS">FIG. 10G</figref>, a plating layer <b>1047</b> (e.g. a blanket metal) is formed (for example by sputtering the blanket metal) on the top surface of the substrate <b>1045</b>, thereby covering this top surface and making electrical contact with contact element <b>1046</b>. A photoresist layer is deposited and patterned to leave openings in the photoresist layer <b>1048</b> over a portion of the plating layer <b>1047</b> and another metal layer <b>1049</b> is formed by plating the metal onto the plating layer <b>1047</b>. <figref idref="DRAWINGS">FIG. 10H</figref> shows the resulting structure. Another photoresist layer is deposited and patterned to create developed photoresist layer <b>1050</b> which has an opening over the metal layer <b>1049</b> as shown in FIG. <b>10</b>I. Then a sputtering mask <b>1052</b> is used to selectively sputter metal layer <b>1051</b> onto a portion of developed photoresist layer <b>1050</b> and onto an exposed portion of metal layer <b>1049</b>. The resulting structure (and the corresponding sputtering mask) are shown in FIG. <b>10</b>J. Another metal layer <b>1053</b> is plated onto the metal layer <b>1051</b> resulting in the structure shown in FIG. <b>10</b>K. Then, the photoresist layers are stripped and portions of the plating layer <b>1047</b> not protected by layer <b>1049</b> are selectively etched to remove all such portions of plating layer <b>1047</b>, resulting in the structure shown in <figref idref="DRAWINGS">FIG. 10L. A</figref> stop structure <b>1055</b> and a tip <b>1054</b> may then be applied respectively to the substrate <b>1045</b> and the resilient contact element as shown in FIG. <b>10</b>M.

0069<figref idref="DRAWINGS">FIG. 11</figref> shows one technique for the use of an interconnect assembly of the present invention. This interconnect <b>1101</b> includes a chuck structure <b>1117</b> disposed above a semiconductor wafer <b>1111</b>, which wafer is supported by a bellows structure <b>1103</b>. The bellows structure <b>1103</b> includes an expandable bellows <b>1105</b> and intake and outtake ports <b>1107</b>A and <b>1107</b>B. In one use of this bellows structure, a fluid, such as water <b>1106</b> is passed into and out of the bellows structure <b>1103</b>. A thin steel membrane <b>1109</b> is welded or otherwise attached to the bellows <b>1105</b>. The thin membrane may be used to exert uniform pressure against the back of wafer <b>1111</b> to press the top surface of the wafer against the stop structures <b>1121</b> and <b>1123</b>, thereby improving the electrical connections between the springs (or other resilient contact elements) on the wafer and the contact elements on substrate <b>1117</b>. This uniform pressure will typically overcome variations in flatness between the meeting surfaces, such as the top surface of the wafer <b>1111</b> and the surface supporting the stop structures <b>1121</b> and contact elements <b>1125</b> and <b>1127</b>. This thin steel membrane <b>1109</b> also allows for the transfer of heat to or from the semiconductor wafer <b>1111</b> which is disposed on top of the membrane <b>1109</b>. The fluid, such as water <b>1106</b>, may be introduced into the bellows structure under pressure to force the membrane <b>1109</b> into direct contact with the backside of the wafer <b>1111</b>.

0070This fluid may be heated or cooled in order to control or effect the temperature of the wafer. For example, in a burn-in test, the fluid may be heated to raise the temperature of the wafer and then cooled over several cycles. The chuck <b>1117</b> includes stop structures <b>1121</b> and <b>1123</b> which are proximally adjacent to contact elements <b>1125</b> and <b>1127</b> respectively. It may be desirable to place a thermal transfer layer between the membrane <b>1109</b> and the back of the wafer <b>1111</b> to improve the heat transfer efficiency between the fluid and the wafer <b>1111</b>. The contact elements <b>1125</b> and <b>1127</b> are designed to make contact with the resilient contact elements <b>1115</b> and <b>1113</b> on the wafer <b>1111</b>. It will be appreciated that there will typically be many more resilient contact elements and many more contact elements than those shown in FIG. <b>11</b>. The chuck <b>1117</b> includes wiring or other interconnection in order to connect resilient contact elements <b>1115</b> and <b>1113</b>, through contact elements <b>1125</b> and <b>1127</b>, to a tester allowing communication of power, signals, and the like between the tester and the semiconductor wafer. The chuck <b>1117</b> may be held in place by a post <b>1118</b> in order to allow the wafer <b>1111</b> to be pressed against the chuck <b>1117</b> by the expanding of the bellows <b>1105</b>; alternatively, the chuck <b>1117</b> may be pressed and held by a clamshell support which contacts and covers the top of the chuck <b>1117</b> with a backing plate and may also surround the sides and bottom of the bellows <b>1105</b>.

0071<figref idref="DRAWINGS">FIG. 12A</figref> shows another example of an interconnect assembly <b>1201</b> according to the present invention. In this case, a chuck <b>1203</b> supports a wafer of semiconductor devices <b>1204</b>. The wafer includes a plurality of contact elements, such as the contact element <b>1210</b>A which are designed and disposed to make contact relative to resilient contact elements on the wiring substrate <b>1206</b>. The resilient contact elements <b>1207</b>, <b>1209</b>, and <b>1210</b> are another example of a resilient element; in this case, they have a generally straight cantilever structure. The stop structures <b>1214</b>, <b>1216</b>, and <b>1218</b> are attached to the wiring substrate <b>1206</b> and are designed to define the z separation between the wiring substrate <b>1206</b> and the wafer <b>1204</b>. A vacuum port <b>1212</b> in the wiring substrate <b>1206</b> allows a vacuum to be formed between the space between the wiring substrate <b>1206</b> and the chuck <b>1203</b>. The o-ring seal <b>1205</b> ensures that a vacuum is formed between the wiring substrate <b>1206</b> and the chuck <b>1203</b>. When the vacuum is formed, the wiring substrate <b>1206</b> is pressed down towards the wafer <b>1204</b> in order to cause contact to be made between the various resilient contact elements and their corresponding contact elements on the wafer <b>1204</b>.

0072<figref idref="DRAWINGS">FIG. 12B</figref> shows another example of an interconnect assembly <b>1251</b> according to the present invention. In this case, a pressure bladder <b>1255</b> forces the wiring substrate <b>1254</b> in contact with the wafer <b>1253</b>. A clamp <b>1255</b>A is used to press the bladder in substrate <b>1254</b>. The wafer <b>1253</b> sits on top of a chuck <b>1252</b> and includes a plurality of contact elements, such as the contact element <b>1257</b>A shown in FIG. <b>12</b>B. As the bladder <b>1255</b> forces the wiring substrate <b>1254</b> into contact with the wafer <b>1253</b>, the stop structures <b>1258</b>, <b>1259</b>, and <b>1260</b> are brought into contact with the top surface of the wafer <b>1253</b>. This contact defines a separation between the wiring substrate <b>1254</b> and the semiconductor wafer <b>1253</b>. When this contact occurs, the resilient contact elements <b>1257</b> are brought into mechanical and electrical contact with their corresponding contact elements on the wafer <b>1253</b>.

0073<figref idref="DRAWINGS">FIG. 13</figref> shows an example of an interconnect assembly <b>1301</b> which includes a stop structure <b>1310</b> that houses a circuit element, in this case a capacitor, which is coupled to circuitry in the integrated circuit of the substrate <b>1302</b>. The stop structure <b>1310</b> is designed to define the minimum vertical separation between the substrate <b>1302</b> and the substrate <b>1303</b> when the resilient contact elements <b>1304</b> and <b>1305</b> are brought into mechanical and electrical contact with their corresponding contact elements <b>1306</b> and <b>1307</b> in the substrate <b>1302</b>. The contact elements <b>1307</b> and <b>1306</b> are contained within an insulating material <b>1308</b> which may be a conventional dielectric material used in fabricating integrated circuits. It will be appreciated that the interconnection to various other circuit elements within the integrated circuit in the substrate <b>1302</b> is not shown in <figref idref="DRAWINGS">FIG. 13</figref>, which is a cross-sectional view through the stop structure <b>1310</b> and the substrate <b>1302</b>. The stop structure <b>1310</b> is a multilayer structure including several dielectric layers and several conductive layers which may be metal layers. In the example shown in <figref idref="DRAWINGS">FIG. 13</figref>, metal (or other conductive) layers <b>1314</b> and <b>1318</b> are separated by an insulating layer <b>1316</b> to form a capacitor. The metal layers <b>1314</b> and <b>1318</b> as well as the insulating layers <b>1316</b> and <b>1322</b> are encapsulated within an insulating layer <b>1312</b>. The stop structure <b>1310</b> itself may resemble a post or cylinder or other shapes (e.g. rectangular, arbitrary pattern, zig-zag of connected rectangle, etc.) which is completely covered by the encapsulating insulating layer <b>1312</b>. This insulating layer may be a polyimide material or silicon dioxide or other insulator. The metal layer <b>1318</b> is coupled electrically in one embodiment by a solder ball <b>1321</b> to a post or other contact element <b>1320</b> in the substrate <b>1302</b>. The metal layer <b>1314</b> is coupled by a post structure <b>1314</b>A which extends into the substrate <b>1302</b>. In this manner, the capacitor in the stop structure <b>1310</b> is coupled electrically to a circuit element in the substrate <b>1302</b>. It will be appreciated that there will be a number of well known techniques which may be employed in fabricating the stop structure <b>1310</b> to include an electrical element, such as the capacitor. In one example, the post structures <b>1314</b>A and <b>1320</b> may be formed in the substrate <b>1302</b>. Then a dielectric layer <b>1322</b> may be formed and patterned to allow an opening for the solder balls, such as the solder ball <b>1321</b>. Alternatively, a metal layer <b>1318</b> may be sputtered upon the entire surface, filling the opening in the insulating layer <b>1322</b>. Then the metal layer <b>1318</b> is patterned in the form shown in <figref idref="DRAWINGS">FIG. 13</figref>, and another insulating layer is deposited over the metal layer <b>1318</b>. This insulating layer is then patterned to create an insulating layer <b>1316</b> and then another metal layer is deposited upon the surface and patterned to create the metal layer <b>1314</b>. Finally, an insulating layer or other passivating layer is applied and patterned to create the insulating layer <b>1312</b> in order to complete the formation of the stop structure <b>1310</b>.

0074<figref idref="DRAWINGS">FIG. 14</figref> shows another example of an interconnect assembly. This interconnect assembly <b>1401</b> includes two stop structures <b>1404</b> and <b>1405</b>, each of which contain circuit elements which are coupled to electrical circuit elements in the substrate <b>1402</b>. The substrate <b>1402</b> also includes a post or other contact element <b>1403</b>A which is coupled mechanically and electrically to a resilient contact element <b>1403</b>.

0075The stop structure <b>1404</b> includes a ground shield <b>1411</b> which is coupled to a ground bus or other circuit in the substrate <b>1402</b>. As used herein, the term circuit element includes a ground shield or plane. Thus, a stop structure may include a ground shield in accordance with the present invention as shown in FIG. <b>14</b>. The stop structure <b>1414</b> also includes a capacitor having conductive plates <b>1413</b> and <b>1415</b> which are coupled electrically to at least one circuit element in the substrate <b>1402</b>.

0076The stop structure <b>1405</b> also includes a ground shield <b>1421</b> coupled electrically to a ground circuit in the substrate <b>1402</b>. The stop structure <b>1405</b> also includes a capacitor formed by the conducting plates <b>1427</b> and <b>1429</b> which are electrically coupled to at least one circuit element in the substrate <b>1402</b>. In addition, the stop structure <b>1405</b> includes conductive elements <b>1423</b> and <b>1425</b> which provide reference voltages, such as V_ssand V_ddwhich may be bussed through the stop structure to electrical components in the stop structure or to electrical components outside of the stop structure.

0077Further aspects concerning the assemblies of <figref idref="DRAWINGS">FIGS. 13 and 14</figref> may be found in U.S. Pat. application Ser. No. 09/114,589, concurrently filed on Jul. 13, 1998, now issued U.S. Pat. No. 6,330,164, and continuation application Ser. No. 09/971,981, now issued U.S. Pat. No. 6,664,628.

0078It will be appreciated that the foregoing description provides illustrative examples of the present invention and is not intended to provide an exhaustive list of the various materials or methods which may be used in creating the interconnect assemblies of the present invention. For example, while polyimide materials may be used to form the stop structures of the present invention, it will be appreciated that other materials may be used, including photoresist which are capable of producing high aspect ratios and which may be cured and left in place as a mechanical element, such as the photoresist SU8. Alternatively, a fill-cured epoxy sheet or polymeric materials or certain metals may also be used as the materials to create the stop structures. Indeed, the stop structure may be formed from any material which is stable at the desired temperatures to which the structure will be exposed, including testing and/or burn-in environments and the expected use environment. It is anticipated that the stop structures according to the present invention will have a minimum height of about 80 microns, although smaller height stop structures are within the scope of the present invention.

0079In the foregoing specification, the present invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.